KW Parking meter [RE-wrenches]

mlafferty at universalenergies.com mlafferty at universalenergies.com
Tue Mar 2 20:03:30 PST 2004


Keith C asks:

>  They want a "central" pv power station for the "huts/homes". 
>  They also want to allocate the huts "x" amount of KW per month, 
>  and when that is exhausted (say 30 KW), they have to go back to
>  the "government/authority", and purchase more. Anyone run into
>  something like this, or know an inexpensive widget that can
>  accomplish this for this application?

Keith,

I don't know about "inexpensive"... Relative term that it is.  If you're
looking for something "automatic", it sounds like what you're looking
for may something like a "debit card or smart card with a switch" setup.
This application is being used in the Phillipines and other parts of
Asia for solar-powered water pumping in villages.  The villagers pre-pay
to have their cards "filled up" with "x # of gallons".  When they go to
the pumping station to get water, they swipe their cards.  The machine
measures how many gallons they pump and deduct that from their card.
When the card is exhausted, the "customer" must go ante up to get their
card "re-charged" so they can get more water.  I called a very trusted
friend of mine regarding your proposed application to get a starting
point regarding the "brains behind the mechanism" and some
recommendations.  Two hours later, I know way more about different ways
to approach the "automatic payment / metering" aspect than I ever
thought about before... LOL

There are too many options to lay out here, especially considering that
I'm no expert with this end of the spectrum.  He recommended two
companies by name.  Links follow: http://www.gemplus.com/  and
http://www.qitech.com/  if you're thinking of going this route.  A fair
amount of interesting stuff came up on google when I entered < prepaid
electricity card >  Most of it looks expensive and requires
infrastructure.

In addition to the "brains / metering" stuff, you will need to
incorporate some type of contactor in the main feeder line to each
"hut/home".  The size and rating of that piece would be dependent on
voltage, max design load, etc.  

In looking at this with the limited information provided, I am inclined
to think that, since there is / will be a central "authority" to accept
payments and be responsible for operating the system anyway, installing
a basic kWH meter and manual-lockable disconnect for each hut would
prove the most cost-effective and reliable setup.  "Customers" could
pre-pay for whatever baseline was established by the community, with
that amount kept as a "deposit".  After reading the meters on an
established schedule, accounts would be settled regarding the
difference.  Much like a standard utility company.... As much as I hate
to say it.

Unless there is a significant amount of money to invest in setting up a
high-tech, "automated" system, with its potential for reliability
issues, why re-invent the wheel?  Assuming these homes don't have power
now and that this is a relatively small village of close proximity and
relationships with relatively low projected kWH consumption, I don't see
why you would want to add complexity to their lives.  Electricity alone
will do that!  

Two Palms and a Hammock!

Matt Lafferty
Universal Energies Institute
mlafferty at universalenergies.com
(916) 422-9772
(916) 628-7694 Cell
(916) 914-2247 Fax
www.universalenergies.com

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